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The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired

Gui-Rong Liu

《结构与土木工程前沿（英文）》 2019年第13卷第2期页码 456-477 doi: 10.1007/s11709-019-0519-5

摘要：

The smoothed finite element method (S-FEM) was originated by G R Liu by combining some meshfree techniques with the well-established standard finite element method (FEM). It has a family of models carefully designed with innovative types of smoothing domains. These models are found having a number of important and theoretically profound properties. This article first provides a concise and easy-to-follow presentation of key formulations used in the S-FEM. A number of important properties and unique features of S-FEM models are discussed in detail, including 1) theoretically proven softening effects; 2) upper-bound solutions; 3) accurate solutions and higher convergence rates; 4) insensitivity to mesh distortion; 5) Jacobian-free; 6) volumetric-locking-free; and most importantly 7) working well with triangular and tetrahedral meshes that can be automatically generated. The S-FEM is thus ideal for automation in computations and adaptive analyses, and hence has profound impact on AI-assisted modeling and simulation. Most importantly, one can now purposely design an S-FEM model to obtain solutions with special properties as wish, meaning that S-FEM offers a framework for design numerical models with desired properties. This novel concept of numerical model on-demand may drastically change the landscape of modeling and simulation. Future directions of research are also provided.

关键词： computational method finite element method smoothed finite element method strain smoothing technique smoothing domain weakened weak form solid mechanics softening effect upper bound solution

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Achieving desired nodal lines in freely vibrating structures via material-field series-expansion topology

《机械工程前沿（英文）》 2023年第18卷第3期 doi: 10.1007/s11465-023-0758-y

摘要： Accurately controlling the nodal lines of vibrating structures with topology optimization is a highly challenging task. The major difficulties in this type of problem include a large number of design variables, the highly nonlinear and multi-peak characteristics of iteration, and the changeable orders of eigenmodes. In this study, an effective material-field series-expansion (MFSE)-based topology optimization design strategy for precisely controlling nodal lines is proposed. Here, two typical optimization targets are established: (1) minimizing the difference between structural nodal lines and their desired positions, and (2) keeping the position of nodal lines within the specified range while optimizing certain dynamic performance. To solve this complex optimization problem, the structural topology of structures is first represented by a few design variables on the basis of the MFSE model. Then, the problems are effectively solved using a sequence Kriging-based optimization algorithm without requiring design sensitivity analysis. The proposed design strategy inherently circumvents various numerical difficulties and can effectively obtain the desired vibration modes and nodal lines. Numerical examples are provided to validate the proposed topology optimization models and the corresponding solution strategy.

关键词： nodal line topology optimization structural dynamics design material-field series-expansion

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Bio-based Waterborne Poly(Vanillin-Butyl Acrylate)/MXene Coatings for Leather with Desired Warmth Retention

Jianzhong Ma,Li Ma,Lei Zhang,Wenbo Zhang,Qianqian Fan,Buxing Han,

《工程（英文）》 doi: 10.1016/j.eng.2023.06.005

摘要： This study presents a solvent-free, facile synthesis of a bio-based green antibacterial agent and aromatic monomer methacrylated vanillin (MV) using vanillin. The resulting MV not only imparted antibacterial properties to coatings layered on leather, but could also be employed as a green alternative to petroleum-based carcinogen styrene (St). Herein, MV was copolymerized with butyl acrylate (BA) to obtain waterborne bio-based P(MV–BA) miniemulsion via miniemulsion polymerization. Subsequently, MXene nanosheets with excellent photothermal conversion performance and antibacterial properties, were introduced into the P(MV–BA) miniemulsion by ultrasonic dispersion. During the gradual solidification of P(MV–BA)/MXene nanocomposite miniemulsion on the leather surface, MXene gradually migrated to the surface of leather coatings due to the cavitation effect of ultrasonication and amphiphilicity of MXene, which prompted its full exposure to light and bacteria, exerting the maximum photothermal conversion efficiency and significant antibacterial efficacy. In particular, when the dosage of MXene nanosheets was 1.4 wt%, the surface temperature of P(MV–BA)/MXene nanocomposite miniemulsion-coated leather (PML) increased by about 15 °C in an outdoor environment during winter, and the antibacterial rate against Escherichia coli and Staphylococcus aureus was nearly 100% under the simulated sunlight treatment for 30 min. Moreover, the introduction of MXene nanosheets increased the air permeability, water vapor permeability, and thermal stability of these coatings. This study provides a new insight into the preparation of novel, green, and waterborne bio-based nanocomposite coatings for leather, with desired warmth retention and antibacterial properties. It can not only realize zero-carbon heating based on sunlight in winter, reducing the use of fossil fuels and greenhouse gas emissions, but also improve ability to fight off invasion by harmful bacteria, viruses, and other microorganisms.

关键词： MXene nanosheets Vanillin Styrene substitute Leather coating Photothermal conversion Warmth retention Antibacterial properties

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Measurement and analysis of typical motion error traces from a circular test

LI Xiaoli, LIU Huanlao

《机械工程前沿（英文）》 2008年第3卷第2期页码 146-150 doi: 10.1007/s11465-008-0033-2

摘要： The circular test provides a rapid and efficient way of measuring the contouring accuracy of a machine tool. To get the actual point coordinate in the work plane, an improved measurement instrument - a new ball bar test system - is presented in this paper to identify both the radial error and the rotation angle error when the machine is manipulated to move in circular traces. Based on the measured circular error, a combination of Fourier components is chosen to represent the systematic form error that fluctuates in the radial direction. The typical motion errors represented by the corresponding Fourier components can thus be identified. The values for machine compensation can be calculated and adjusted until the desired results are achieved.

关键词： machine compensation direction combination desired efficient

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实现“不可行”的共聚反应以构筑氮掺杂多孔碳的理想聚合物前驱体 Article

亓士超, 陆筱杰, 楼寅聪, 周睿, 薛丁铭, 刘晓勤, 孙林兵

《工程（英文）》 2022年第16卷第9期页码 154-161 doi: 10.1016/j.eng.2021.07.031

摘要：

某些预想的概念验证反应虽可能产生具有新功能或新应用潜力的材料，但最终常被证明是不可实现的或从商业角度上是不可行的。为了在溶剂环境中探索未知反应的反应条件，科研人员已付出了大量的努力，也浪费了大量的精力。因为人们普遍相信通过将反应物溶解在溶剂中，可以提高反应物的活性，从而促进反应。本研究发现了一个反常现象：在不同溶剂环境下，1,3,5-三（氯甲基）-2,4,6-三甲基苯与三聚氰胺的共聚反应都是无法实现的，然而利用无溶剂法却可成功地实现该反应。通过第一性原理计算和分子动力学模拟，证明了溶剂反应不具备的两个决定性因素，即由副产物的及时释放所推动的反应平衡和活化单体分子在固相中的受限热运动却可基于无溶剂法实现。由于具有较高的芳香性和氮杂环含量，由无溶剂法得到的共聚物表现出良好的应用潜力，可作为制备氮掺杂多孔碳的前驱体，使氮掺杂多孔碳具有令人满意的碳产率、理想的残氮含量、理想的结构特性，与最近报道的其他代表性同类吸附剂相比，在二氧化碳捕获能力方面展现出竞争潜力。

关键词：无溶剂法溶剂效应共聚反应氮掺杂多孔碳